1. Field of the Invention
The present invention relates to a control device for a fuel cell used for a fuel cell powered vehicle. More specifically, the present invention relates to a control device for a fuel cell which is capable of detecting failure in a hydrogen purge valve disposed at a hydrogen exhaust line of a fuel cell.
2. Description of Related Art
In a fuel cell stack formed by stacking a plurality of PEM type fuel cell units in series, electromotive force is obtained by supplying fuel (i.e., hydrogen) to its anode and an oxidizing agent (e.g., air) to its cathode.
In the above fuel cell, electric power and water is generated by the reaction of hydrogen and oxygen. If the water generated by the reaction is condensed to water drops and remains in a reaction gas passage of the fuel cell unit, the water blocks the reaction gas passage and causes a reduction in the cell output voltage. This phenomenon is called flooding. In order to prevent or eliminate the problem of flooding, the water generated is discharged to the outside when the fuel cell generates power of a certain amount or for a certain period of time, or the cell voltage decreases below a standard voltage. Also, if the water generated is condensed to water drops and blocks the reaction gas passage, the reaction gas is not supplied beyond the water blocking the line. Accordingly, a partial gas shortage is generated, and damage is caused to a solid polymer electrolyte membrane to lower the performance thereof.
In order to carry out the above-mentioned discharge of the generated water to the outside, a hydrogen purge valve is disposed at an anode gas exhaust line of a pressurized hydrogen circulation type fuel cell system, and the water generated by the reaction is discharged to the outside by opening the hydrogen purge valve.